Process for naphtha reforming



y 1966 A. R. BERNAS ET AL 3,262,885

PROCESS FOR NAPHTHA REFORMING Filed Dec. 20, 1961 ARNOLD R. BERNASGEORGE RUSSELL JAMES AGENT United States Patent 0 3,262,886 PROCESS FORNAPHTHA REFORMING Arnold R. Bernas, Nixon, N.J., and George RussellJames,

Armonk, N.Y., assignors to Chemical Construction Corporation, New York,N.Y., a corporation of Delaware Filed Dec. 20, 1961, Ser. No. 160,749 6Claims. (Ql. 252-376) This invention relates to the catalyticsteam-reforming of naphtha, to produce ammonia synthesis gas. A newapproach to naphtha reforming has been developed, in which naphtha iscompletely converted to a synthesis gas stream by externally firedcatalytic steam reform, without concomitant accumulation of free carbon.The formation of lower hydrocarbons by thermal cracking is alsocontrolled and becomes a transient phenomenon, and thus the finalprocess gas stream contains only a negligible proportion of unreactedlower hydrocarbons.

Naphtha is relatively volatile petroleum refining product orintermediate, which is generally defined in terms of boiling range.Thus, according to a crude oil survey in Industrial and EngineeringChemistry, 44, #11 (November 1952), p. 2578, naptha is defined asfollows: Na-phtha content (of crude oil) is the total distillaterecovered in the U.S. Bureau of Mines routine analysis at a vaportemperature of 392 F. A more detailed definition of naphtha appears inPetroleum Refining With Chemicals, by Kalichevsky & Kobe (1956). Adiscussion of naphtha on pp. 21-23 of this text indicates that differentnaphthas may have boiling ranges from a low point of 122 F. to a maximumof 400 F. Thus naphtha is defined as a general term which is applied tofractions boiling in the gasoline or low kerosene range. In generalthen, naphtha is a low-boiling and readily volatilized liquidhydrocarbon cut, derived from crude oil distillation in petroleumrefining. This material consists mostly of straight chain paraffinics inthe 0-5 to C-9 range, however, up to about 30% naphthenics together withup to 10% aromatics and unsaturates may also be present. In addition,naphtha also generally contains a significant proportion of sulfur inthe form of COS and mercaptans.

Naphtha may be utilized in a variety of ways. Thus, crude naphtha may befurther refined and upgraded to yield a variety of finished petroleumsolvents. In many refineries, naphtha is reformed in the petroleum senseof the term. In this case, the crude naphtha is cracked, and hydrocarbonmolecules are reassembled in the presence of platinum or other suitablecatalyst, so as to yield a substantial proportion of branched chain oraromatics molecules. This material is then blended with other refinerycuts for gasoline usage. In the terminology of the present invention,the word reforming has an entirely different meaning, as will appearinfra.

Fin-ally, naphtha may also be utilized as a hydrocarbon raw material forthe manufacture of hydrogen or ammonia synthesis gas. There are twogeneral approaches to the conversion of the various types ofhydrocarbons to synthesis gas, namely, steam reforming and partialoxidation. In steam reforming, a normally gaseous hydrocarbon such asmethane is mixed with steam, and the mixture is then passed through anexternally heated bed of nickel-containing reform catalyst. Anendothermic reaction takes place between the hydrocarbon and steam,resulting in the formation of a synthesis gas product stream containingprincipally hydrogen, carbon monoxide and carbon dioxide.

In the case of partial oxidation, a hydrocarbon raw material is reactedwith oxygen or oxygen-enriched air at a highly elevated temperature. Theproduct stream is then quenched, to yield a crude synthesis gas stream.

'ice

A catalyst is not employed in conventional partial oxidation practice,since essentially complete reaction of the hydrocarbon is readilyaccomplished at the high temper ature levels generated in this process.In addition, a variety of hydrocarbons may be employed in partialoxidation, including liquid or even powdered solid hydrocarbons as wellas gases.

As is well known in the art, catalytic steam reforming is generallylimited to the usage of gaseous hydrocarbons, due to such problems aspartial conversion and carbon deposition, when vaporized liquidhydrocarbons are employed. One approach to the steam reforming of higherhydracorbons such as naphtha is described in U.S. Patent No. 2,940,840.In this process, the formation of free carbon in the catalyst bed ispurposely brought about by overloading the catalyst. Although thisprocess is cyclic and requires a regeneration period during which thedeposited carbon is oxidized for removal, it is claimed that the overallprocess efficiency is better than in prior practice. Another recentapproach to the problem is described in U.S. Patent 2,943,062. A partialoxidation effect is obtained in a catalytic process by adding oxygen toa stream of hydrocarbon vapor or partially reformed gas, immediatelybefore the stream is passed through a catalyst bed. The bed is notexternally heated, instead the process is carried out in arefractory-lined chamber as in conventional partial oxidation. It willbe evident that this procedure is subject to the principal economicdrawback of all partial oxidation processes, namely, that an airseparation plant is required.

In the present invention, naphtha is catalytically steamreformed toproduce an ammonia synthesis gas. Thus, a limited amount of process airis employed in the present invention to assist in the gasification ofthe naphtha prior to catalytic reform, as well as to provide thenitrogen gas component for subsequent ammonia synthesis. The process ofthe present invention depends on a unique balance of reaction conditionsto achieve the catalytic steam reforming of naphtha, since this isacomplished without accumulated deposition of free carbon. In addition,no significant amount of unreacted hydrocarbon is present in the finalsynthesis gas. The process is carried out in two stages, agasification-condition stage and a catalytic steam reform stage. Thesestages of the process are distinctly co-acting and dependent, in that ithas been found that the conditioning stage must be of short duration inorder to prevent the reactants from reaching equilibrium with resultantdeposition of free carbon in the catalyst bed. It has also been foundthat the reactants must be preheated in order to provide a minimumtemperature level in the conditioning stage. Thus, in the presentinvention, process streams of naphtha, steam and air are preheated andmixed. A partial reaction ensues, and the mixed process stream, nowcontaining a variety of intermediate components but not in finalreaction equilibrium, is passed through an externally heated bed ofreform catalyst. A final process stream is produced by steam reformingof residual naphtha and intermediate lower hydrocarbons. This finalprocess stream consists of a synthesis gas containing principallyhydrogen, nitrogen, carbon monoxide and carbon dioxide. The stream isessentially free of unreacted hydrocarbons or solid particulate carbon.

The process of the present invention possesses several significantadvantages. A primary advantage is that naphtha is catalytically steamreformed to ammonia synthesis gas, without the concomitant accumulationof free carbon or tars, and without the production of lower hydrocarbonsas a significant component of the final process stream. Thus, no recycleor side stream disposal is required. The process is continuous ratherthan cyclic or intermittent.

In addition, one major economic cost in partial oxidation processes,namely an air separation plant or other source of free oxygen, is notrequired in the process of the present invention. Finally, conventionalsteam reformer apparatus rather than a special or costly apparatusdesign may be employed in the catalytic reforming stage of the presentinvention,

It is an object of the present invention to produce a synthesis gas forusage in ammonia production by steam reform of naphtha.

Another object is to reform naphtha in a continuous process, withoutaccumulated deposition of tars or free carbon.

A further object is to reform naphtha by catalytic reaction with steam.

An additional object is to react naphtha with steam and air by atwo-stage mixing and catalytic reform process, whereby naphtha iscompletely reformed and a gas stream principally containing hydrogen,nitrogen, carbon monoxide and carbon dioxide is produced.

Still another object is to gasify and reform naphtha to an ammoniasynthesis gas using only air, rather than free oxygen or oxygen-enrichedair.

These and other objects and advantages of the present invention willbecome evident from the description which follows. Referring to thefigure, stream 1 is a liquid naphtha, derived from petroleum refining orother types of crude oil processing. Thus, as described supra, stream 1consists principally of paraflinic hydrocarbons in the C to C-9 range,together with naphthenics as well as minor amounts of aromatics andsulfur compounds. The liquid stream 1 is vaporized and preheated inheater 2, to form naphtha vapor stream 3. Vapor stream 3 may be producedat any suitable temperature, ranging from the boiling point of naphthaup to about 1000" F. Above this temperature level the naphtha vapor maybecome unstable, and certain portions or components will readily crackto smaller molecules with concomitant carbon deposition. Stream 3 thusis preferably produced at a temperature ranging from 400 F. to 800 F.

Stream 4 consists of highly superheated steam, preheated usually to atemperature above 1500 F., and preferably to the range of 1500 F. to1700 F. Although lower ratios are feasible, it has been found that arange of molar steam/carbon ratios between 3 to 1 and 6 to 1 isdesirable in proportioning the relative flow rates of streams 4 and 3,in order to prevent accumulated deposition of carbon under normaloperating conditions.

Stream 5 consists of air, preheated usually to a temperature above 800F., and preferably to the range of 800 F. to 1200 F. The proportion ofair employed in the process is quite small, thus only enough air is usedto provide a 3 to 1 molar ratio of hydrogen to nitrogen in the finalammonia synthesis gas. The streams 4 and 5 are preferably combined, toform a mixed steam-air stream 6 at a temperature of at least 1100 F.Stream 6 is now combined with naphtha vapor stream 3, and the mixedstream 7 is immediately passed into residence or gas conditioningchamber 8. It will be appreciated that streams 3, 4 and 5 may beseparately passed into chamber 8, however prernixing of the air andsteam to form stream 6 is a preferable procedure since this results inbetter and more rapid mixing of the several streams. Thus, stream 3 ismore rapidly dispersed and diluted due to the mixing with stream 6,prior to entry of the naphtha vapor into residence chamber 8.Consequently, the possibility of transient carbon formation ordepositiondue to cracking of the naphtha is reduced by the pre-mixing step.

In chamber 8, simultaneous reactions take place between and among theseveral reactants and intermediate components. The temperature of theprocess stream immediately rises, due to exothermic combustion of aportion of the naphtha with the oxygen content of the air. In addi tion,a portion of the naphtha is non-catalytically steam reformed due to thehigh temperature and high steam concentration in chamber 8. Thisendothermic reaction serves to produce free hydrogen, and also moderatesthe temperature rise due to combustion. A further portion of the naphthais thermally cracked to lower hydrocarbons, due also to the hightemperature level. However, simultaneous deposition and accumulation offree carbon does not instantaneously occur. Instead, the unstable lowerhydrocarbons are selectively hydrogenated to a certain extent due to thein situ formation of hydrogen, which may possibly be formed in thenascent state. Thus, the resultant gaseous stream 9 contains significantproportions of steam, nitrogen, hydrogen, carbon dioxide, carbonmonoxide, unsaturated hydrocarbons (mostly ethylene), methane andethane. It should be understood however, that these components arepresent on a transient or instantaneous basis. If stream 9 is allowed toreach stable equilibrium under these process conditions, significantformation and accumulated deposition of free carbon will take place.

Under some conditions, the temperature in unit 8 may be in the range of1450 F. to 1500 F. However, with such low reaction temperatures, theformation of free carbon may readily occur, especially after all theresidual free oxygen is consumed, unless the residence time is kept inthe range of 0.05 to 0.33 second. With such short residence times,unreacted naphtha may pass into the following catalytic stage of theprocess, however, as will appear infra, the formation of free carbon isreadily prevented in the catalyic stage by maintenance of a temperaturelevel above 1600 F. In general, the residence time in chamber 8 must bekept below 1.0 second, and preferably in the range of 0.05 to 0.33second,'in order to achieve the desired reactions without carbonformation. In addition, the instantaneous mix temperature of stream 7must be kept above 1000 F., since it has been found in practice that thevarious competing reactions will tend to form free carbon if the initialmix temperature is below 1000 F. This initial or instantaneous mixturetemperature should preferably be in the range of 1400 F. to 1700 F., inorder to preclude carbon formation due to process upsets. It will beevident that chamber 8 may actually, in terms of apparatus design,consist merely of an insulated pipe section extending between the pointof mixing of the reactant streams and the entry of the conditioned gasstream into the catalyst bed section.

Stream 9 now passes into the catalytic reformer unit 10. Reformer 10 maybe a unit of conventional design, such as shown in US. Patent 2,660,519.Thus, unit 10 is provided with a plurality of reformer tubes such as 11having a bed or charge of reform catalyst 12, usually consisting ofnickel or cobalt deposited on a suitable carrier. Tube 11 is externallyheated by such means as combustion of fluid hydrocarbon streams 13 withair streams 14, with flue gas removal via 15.

As mentioned supra, it has been found that the temperature of thecatalyst in bed 12 must generally be kept above 1600 F., in order toprevent carbon accumulation. An exception to this general requirement of1600 F. minimum temperature during catalytic reforming is the case wherestream 9 contains unreacted free oxygen. Free oxygen could be present instream 9 if residence time in unit 8 is kept very short. Under suchcircumstances, stream 9 and the initial portion of bed 12 in which freeoxygen is present may be maintained at a lower temperature level, downto 1400 F., without concomitant accumulated deposition of free carbon.Of course, after all free oxygen is consumed, the catalyst bed mustthereafter be kept at 1600 F. or higher to prevent carbon deposition. Asthe process stream 9 passes into bed 12, endothermic steam reforming ofhydrocarbons immediately takes place. In order to prevent a concomitantsudden drop in the in situ process temperature at the inlet end of bed12, the equivalent linear velocity of the process stream in the bed 12is maintained above 5 ft./second. Equivalent linear velocity refers tothe gas velocity which would exist at normal operating conditions, ifthe tube was not filled with catalyst. It has been determined that thislinear velocity should preferably be in the range of ft./ sec. to 30ft./sec., in order to effectively spread out the reforming reactionthrough the bed 12 and thereby effectively prevent carbon deposition.Various other expedients may be adopted in this respect. Thus, theapparatus concept embodied in US. 2,801,159 may alternatively beemployed in the present invention in order to more effectively dispersestream 9 into bed 12. Other modifications, such as diluting the upperportion of catalyst bed 12 with inert material such as porcelain, so asto reduce the amount of hydrocarbon reformed per unit volume ofcatalyst, may also be adopted in order to extend the reforming reactionsthrough bed 12 and thereby prevent localized temperature decrease andconcomitant carbon deposition.

The resultant reformed gas stream is removed from tube 11 via 16. Stream16 contains essentially only hydrogen, nitrogen, carbon monoxide, carbondioxide and steam. A typical analysis of stream 16 (Table I infra, run#12) was as follows: 51.4% hydrogen, 22.5% nitrogen, 13.0% carbondioxide, 12.1% carbon monoxide, 1.0% methane and 0.0% unsaturates. Thisanalysis was on a dry basis, the total product stream generallycontained about 50% steam on a total volume basis. In order to produce afinished ammonia synthesis gas with a 3:1 ratio of hydrogen to nitrogen,stream 16 is now processed by conventional technology, not shown. Thiswill include the usual process steps of CO-oxidat-ion, carbon dioxideremoval, etc. It -will be understood that the process of the presentinvention may be carried out with other proportions of air, besides thatwhich will yield a final 3 :1 ratio of hydrogen to nitrogen. In somecases, such as when stream 16 is to be employed as a reducing gas, theproportion of air will not necessarily be exactly such as to yield afinal 3:1 ratio. Somewhat more air may be employed in such cases, sincea higher proportion of nitrogen in the final product gas will not beobjectionable. Using relatively more air in the process of the presentinvention is advantageous since lower preheat temperatures are requiredand further since the possibility of carbon deposition due to processupsets is lessened. Depending on the purity and carbon forming tendencyof the particular naphtha, it will also be possible in some cases todecrease the ratio of .air employed in the process without depositingcarbon in the catalyst bed. In this case, equipment size is reduced anda richer gas is produced. If the product gas is to be employed inammonia synthesis, further nitrogen may be added at a later stage of theprocess, preferably after carbon dioxide removal.

It has been found that operating pressure does not appear to be asignificant variable in the process of the present invention. Althoughpressure is not critical, an operating pressure in the range of 100p.s;i.g. to 300 p.s.i.g. is preferable since reform plant equipment sizeis reduced, and also because subsequent compression costs are reduced.In addition, reforming at elevated pressure yields a high pressureprocess gas which thus may be directly treated for carbon dioxideremoval by hot potassium car bonate scrubbing.

It will be evident to those skilled in the art that the significantprocess variables in steam reforming of naphtha according to the presentinvention are closely inter-related. Thus, the required minimum preheattemperatures of the reactant streams prior to chamber 8 will dependprincipally on the residence time in 8 prior to entry of the mixedstream via 9 into bed 12. With lower residence times in the range of0.05 to 0.10 second, it has been found that the process may besuccessfully carried out with a residence chamber temperature in therange of 1450 F. to 1500 F. However, if a longer residence interval upto 1.0 second is required, then the initial streams 3, 4 and 5 must bepreheated to higher levels so as to provide a temperature range of 1650"F. to 1690 F. in chamber 8, in order to prevent accumulated depositionof free carbon in actual operation of the process.

Similarly, it will be recognized that .a minimum steam/ carbon ratio of3:1 is generally required, in order to satisfy material balanceconsiderations by providing suflicient steam for complete reaction withthe naphtha. However, a steam/carbon ratio in the range of 5:1 to 721has been found to be optimum in providing complete reaction,satisfactory reaction rate, and minimum tendency for carbon formationdue to process upsets. Higher proportions of process air will generallybe required if minimum steam/ carbon ratios are adopted, in order toprevent carbon deposition.

Following are tabulations of various pilot plant runs, which formed thebasis for establishing the critical aspects and ranges which are-thenovel features of the present invention. Table I provides typicaloptimum conditions for essentially carbon-free operation, while Table IIis a tabulation of various runs in which carbon formation andaccumulated deposition was a significant factor. A thin coating ofcarbon was found on the catalyst in many of the runs in Table I,however, this coating did not result in any accumulated deposition orbuildup of free carbon on the catalyst. Apparently the steam-carbonreaction rate in these runs was equal to or faster than the carbonformation rate. In any case, it was found that process equilibrium wasattained without accumulated deposition of carbon. Thus runs #5 and #6in Table I infra were carried out under susbtant-ially identicalconditions. Run #5 was of 49 hours duration while run #6 was extended to269 hours duration. Analysis showed no accumulation of carbon in thecatalyst after run #6, as compared to the catalyst after run #5.

TABLE I.CAIALYTIC STEAM REFORMING OF PETROLEUM NAPHTHA-OPTIMUMCONDITIONS Feed Rates Reforming Temp. F.) Run N0. Inlet PressureResidence Lin a (p.s.i.g.) Time (seconds) Velocity, Naphthn Steam(s.c.l.l1.) Air (s.c.f.h.) In Out ft./sec.

0. 15 150 23 15 0. 028 1, 400 1, 600-1, 650 17-19 0. 21 500 30 75 0.051, 400-1, 500 1, 600-1, 650 16-17 0. 44 320 so 75 0. 033 1, 4404, 480 1,15 0. 44 375 0. 13 1, 400-1, 500 1, 600-1, 650 15 0. 92 700 150 O. 03 1,430-1, 490 1, 600-1, 640 15 0. 92 700 120 150 0.03 1, 430-1, 500 1,600-1, 650 15 0. 92 700 120 150 0; 24 1, 600-1, 650 1, 625-1, 650 15 0.92 700 120 150 0. 24 1, 630 1, 650 15 1. 2 l, 000 150 250 0. 32 1,575-1, 630 1, 630-1, 650 13 O. 92 700 0. 27 1, 610-1, 670 1, 650-1, 67015 0.72 700 110 150 0.27 1, 60 -1, 615 1, 650-1, 660 15 1. 2 1, 000 1500.30 1, 640 1, 605 15 1. 15 1,000 155 150 0. 33 1, 650-1, 665 1, 700-1,775 5 6 1. 15 1,000 155 150 0. 33 1, 640-1, 620 600 15 Negligible orslight carbon formation.

TABLE II.-CATALYTIC STEAM REFO RMING OF PETROLEUM NAPHTHA-MISCELLANEO USRUNS Feed Rates Reforming Temp. F.) Run No. Inlet Pressure ResidenceLinear (p.s.i.g.) Time (seconds) Velocity, Naphtha Steam (s.c.f.h.) Air(s.c.f.h.) In Out ft./see.

Moderate or heavy carbon formation.

Following are analyses of the two commercial naphthas employed in theabove runs. All runs employed naphtha A, except for run #12 of Table Iin which naphtha B was tested. It is evident from the fact that naphthaB was also successfully reformed, that naphthas of varying compositionsand analyses may be successfully reformed by suitable selection ofprocess variables within the scope of the present invention.

The test equipment was modified in order to withdraw a test sample ofthe gas in the residence chamber. In this case, the operating conditionsof run #7 of Table I were employed, with the gas sample being withdrawnat 0.20 second residence time and quenched. Inlet temperatures of thereactant streams to the residence chamber were as follows:

Steam 1675-1680 Air 9404000 Naphtha 600-700 Analysis of the residencechamber gas (dry basis) 0.20 second residence time was as follows(volume Sample #1 Sample #2 Carbon dioxide- Carbon monoxide Unsaturatedhydrocarbons Methane Ethane- Hydrogem- 1 Nitrogen 46 45 Percent ofNaphtha gasified 95 97 Adiabatic temp. F) 1, 690 1, 730

Mostly ethylene.

At a lower inlet steam temperature of 1600 F., the adiabatic temperatureat 0.20 second residence time was in the range of 1630-1690 F.

From the above analyses of the gas stream in the residence chamber,certain conclusions may be reached with respect to probable reactionmechanism. Thus, since no oxygen is present, combustion of naphtha hasalready taken place to completion at 0.20 second. Since some unsaturatesas well as ethane and methane are present, it is evident that somethermal cracking of naphtha also took place, probably together with somehydrogenation of unstable free radicals and unsaturated carbon linkages.This thermal cracking thus was accomplished without carbon accumulation.Finally some free hydrogen is also present hence non-catalytic (thermal)steam reform of naphtha also took place.

Thus, the competing reactions of naphtha combustion, cracking and steamreform are carried out in the first stage of the process of the presentinvention. It has been determined that, by maintenance of reactionconditions within certain critical ranges, these competing reactions maybe carried out without carbon accumulation. In addition, the resultingunstable process stream, when passed to catalytic steam reforming beforefurther reaction ensues, is successfully steam reformed to yield furtherhydrogen and carbon monoxide in a second stage without carbonaccumulation. In summary, the present invention essentially accomplishesthe steam reforming of naphtha by a process which partially gasifies thenaphtha vapor using preheated air and steam. It has been determined thatthe resulting mixed gas stream may be successful-ly converted to asynthesis gas by conventional endothermic catalytic steam reformingwithout accumulater deposition of carbon, if the mixed gas stream ispassed into contact with a catalyst bed before final process equilibriumis reached. Thus, as discussed supra, the critical features of thepresent invention essentially involve the maintenance of the severalinter-related process variables within operating limits in which the newresult of the present invention is achieved, namely the continuous steamreforming of naphtha. As indicated supra, the

' process of the present invention may be employed to produce a reducinggas or other product gas stream with varying proportions of hydrogen andnitrogen, by varying the initial proportion of air. The lower limit ofair employable will depend, in any specific instance, on the carbonforming tendency of the particluar naptha to be reformed and thus willbe empirically determined in practice.

We claim:

1. Process of making a hydrogen-nitrogen gas stream by reforming naphthawhich comprises vaporizing and preheating naphtha to a temperature below1000 F., superheating steam, and preheating air, combining said streamsof naptha, steam and air to form a mixed gaseous stream at a temperatureof at least 1000 F., said mixed gaseous stream having a steam/ carbonmolar ratio of at least 3 to 1 and containing at least 125 standardcubic feet of air per liquid feed stream gallon of naphtha, reactingsaid mixture non-catalytically for an interval less than 1.0 secondwhereby said naphtha is simultaneously oxidized, cracked and partiallyreformed without accumulated deposition of free carbon, andcatalytically reforming the resulting gas mixture in contact with areform catalyst selected from the group consisting of nickel and cobaltdeposited on a carrier, said gas mixture having a linear velocity of atleast 5 ft./sec., said catalyst being externally heated to maintain areaction temperature of at least 1400 F., whereby a final reformed gasmixture substantially free of hydrocarbons and comprising hydrogen,nitrogen, steam, carbon monoxide and carbon dioxide is produced, withoutaccumulated deposition of free carbon.

2. Process of making gas mixture principally containing hydrogen andnitrogen by the continuous reforming of naphtha which comprisesvaporizing a liquid naphtha feed stream, preheating the resultingvaporized naphtha to a temperature of 400 F. to 800 F., preheating airand superheating steam, combining said streams of naphtha, steam and airto form a mixed gaseous stream at a temperature of 1400 F. to 1700 F.and pressure in the range of 100 to 300 p.s.i.g., said mixed gaseousstream having a steam/ carbon molar ratio between 5 to 1 and 7 to 1 andcontaining at least 125 standard cubic feet of air per liquid feedstream gallon of naptha, reacting said mixture non-catalytically for atime interval between 0.05 to 0.33 second, whereby said naphtha issimultaneously oxidized, cracked and reformed without accumulation offree carbon, and catalytically reforming the resulting gas mixture incontact with an externally heated reform catalyst selected from thegroup consisting of nickel and cobalt deposited on a carrier, saidcatalyst being maintained at a reaction temperature of at least 1600 F.,said gas mixture having a linear gas velocity in the range of 10 to 30ft./sec. during said catalytic reform, whereby a final reformed gasmixture is produced without accumulation of free carbon, said gasmixture being substantially free of residual hydrocarbons and comprisinghydrogen, nitrogen, steam, carbon monoxide and carbon dioxide.

3. Process of claim 2, in which said catalyst is disposed in a bedhaving progressively increasing catalytic activity per unit volume ofbed in the downstream direction of gas flow.

4. Process of claim 3, in which said bed is vertically oriented and saidmixed gas stream is passed downwards through the bed.

5. Process of claim 2, in which said streams of naphtha, steam and airare combined by first mixing together the steam and air to form a firstmixed stream at a temperature of at least 1100 F., and thereaftercombining said first mixed stream with the vaporized naphtha.

6. A process of making an ammonia synthesis gas mixture principallycontaining hydrogen and nitrogen in a molar ratio of about 3 to 1 by thecontinuous reforming of naphtha which comprises vaporizing liquidnaphtha, preheating the resulting vaporized naptha to a temperature inthe range of 122 F. to 1000 F., preheating an air stream, superheating astream of steam, combining said stream-s of vaporized naphtha, steam andair to form a mixed gaseous stream at a temperature in the range of 1000F. to 1700 F., said mixed gaseous stream having a steam/carbon molarratio of between 3/1 to 7/1, re-

acting said mixture non-catalytically for a time interval less than 1.0second whereby said vaporized naphtha is simultaneously oxidized,cracked and partially reformed without accumulation of free carbon,catalytically reforming the resulting gas mixture in contact with anexternally heated reform catalyst selected from the group consisting ofnickel and cobalt deposited on a carrier, said gas mixture having alinear gas velocity of at least 5 ft./ sec. during said catalyticreform, said catalyst being maintained at a reaction temperature of atleast 1400 F., whereby a reformed gas mixture is produced substantiallyfree of hydrocarbons and comprising hydrogen, nitrogen, steam, carbonmonoxide and carbon dioxide, catalytically reacting the carbon monoxidecontent of said reformed gas mixture with steam to produce furtherhydrogen by CO-oxidation, and removing carbon dioxide from the resultingprocess gas stream to produce ammonia synthesis gas, the ratio of saidair stream to said vaporized naphtha being proportioned so as to obtaina final hydrogen to nitrogen molar ratio in said ammonia synthesis gasstream of about 3 to 1.

References Cited by the Examiner UNITED STATES PATENTS 2,135,694 11/1938Bardwell et al. 252-376 2,940,840 6/1960 Shapleigh 48-215 3,042,5077/1962 Hilgers 48215 LEON ZITVER, Primary Examiner.

JULIUS GREENWALD, Examiner.

K. VERNON, H. T. MARS, Assistant Examiners.

6. A PROCESS OF MAKING AN AMMONIA SYNTHESIS GAS MIXTURE PRINCIPALLYCONTAINING HYDROGEN AND NITROGEN IN A MOLAR RATIO OF ABOUT 3 TO 1 BY THECONTINUOUS REFORMING OF NAPHTHA WHICH COMPRISES VAPORIZING LIQUIDNAPHTHA, PREHEATING THE RESULTING VAPORIZED NAPTHA TO A TEMPERATURE INTHE RANGE OF 122*F. TO 1000*F., PREHEATING AN AIR STREAM, SUPERHEATING ASTREAM OF STEAM, COMBINING SAID STREAMS OF VAPORIZED NAPHTHA, STEAM OFSTEAM, COMBINING A MIXED GASEOUS STREAM AT A TEMPERATURE IN THE RANGE OF1000*F. TO 1700*F., SAID MIXED GASEOUS STREAM HAVING A STEAM/CARBONMOLAR RATIO OF BETWEEN 3/1 TO 7/1, REACTING SAID MIXTURENON-CATALYTICALLY FOR A TIME INTERVAL LESS THAN 1.0 SECOND WHEREBY SAIDVAPORIZED NAPHTHA IS SIMULTANEOUSLY OXIDIZED, CRACKED AND PARTIALLYREFORMED WITHOUT ACCUMULATION OF FREE CARBON, CATALYTICALLY REFORMINGTHE RESULTING GAS MIXTURE IN CONTACT WITH AN EXTERNALLY HEATED REFORMCATALYST SELECTED FROM THE GROUP